No Second Troy, Yeats

Why should I blame her that she filled my days
With misery, or that she would of late
Have taught to ignorant men most violent ways,
Or hurled the little streets upon the great,
Had they but courage equal to desire?         5
What could have made her peaceful with a mind
That nobleness made simple as a fire,
With beauty like a tightened bow, a kind
That is not natural in an age like this,
Being high and solitary and most stern?  10
Why, what could she have done being what she is?
Was there another Troy for her to burn?

~William Butler Yeats, 1893

Helen of Troy was Helen of Sparta, Daughter of Zeus and Leda.  Leda and Helen were born together 

Painted by Cesare da Sesto after a lost painting by Leonardo da Vinci, 1505-1510, Oil on Panel,
Wilton House, Salisbury

In the form of a swan, the king of gods was chased by an eagle, and sought refuge with Leda. The swan gained her affection, and the two mated. Leda then produced an egg, from which Helen emerged. In this version two eggs came from the union, one with Caster and Pollux and one with Helen and Clytemnestra. Throughout Greek mythology the stories vary, but Menelaus was chosen to be Helen's husband and their marriage was the beginning of the age of heroes.    Helen would leave Sparta with Paris, a prince of Troy some stories say by force, some by persuasion, and some by love but they all end the same - with Helen of Troy being the spark needed for Menelaus and Agamemnon to gather the other kings against Troy and eventually burn Troy after the killing of the King of Troy Priam and Paris' brother Hector as well as the death of Achilles by the hand of Paris with Apollo's help or by Apollo disguised as Paris (depending on which version of the myths you read).

Venus preventing her son Aeneas from killing Helen of Troy, (Luca da Reggio) Ferrari, c. 1650,  Oil On Canvas, 128.3 x 169.5 cm, Art Gallery ofSouth Australia, Copyright @ Art Gallery of South Australia